Cystatin M suppresses the malignant phenotype of human MDA-MB-435S cells

Identification of plasma proteins associated with oesophageal cancer chemotherapeutic treatment outcomes using SWATH-MS

Oesophageal adenocarcinoma (OAC) is an aggressive cancer with a five-year survival of <15%. Current chemotherapeutic strategies only benefit a minority (20-30%) of patients and there are no methods available to differentiate between responders and non-responders. We performed quantitative proteomics using Sequential Window Acquisition of all THeoretical fragment-ion spectra-Mass Spectrometry (SWATH-MS) on albumin/IgG-depleted and non-depleted plasma samples from 23 patients with locally advanced OAC prior to treatment. Individuals were grouped based on tumour regression (TRG) score (TRG1/2/3 vs TRG4/5) after chemotherapy, and differentially abundant proteins were compared. Protein depletion of highly abundant proteins led to the identification of around twice as many proteins. SWATH-MS revealed significant quantitative differences in the abundance of several proteins between the two groups. These included complement c1q subunit proteins, C1QA, C1QB and C1QC, which were of higher abundance in the low TRG group. Of those that were found to be of higher abundance in the high TRG group, glutathione S-transferase pi (GSTP1) exhibited the lowest p-value and highest classification accuracy and Cohen's kappa value. Concentrations of these proteins were further examined using ELISA-based assays. This study provides quantitative information relating to differences in the plasma proteome that underpin response to chemotherapeutic treatment in oesophageal cancers. SIGNIFICANCE: Oesophageal cancers, including oesophageal adenocarcinoma (OAC) and oesophageal gastric junction cancer (OGJ), are one of the leading causes of cancer mortality worldwide. Curative therapy consists of surgery, either alone or in combination with adjuvant or neoadjuvant chemotherapy or radiation, or combination chemoradiotherapy regimens. There are currently no clinico-pathological means of predicting which patients will benefit from chemotherapeutic treatments. There is therefore an urgent need to improve oesophageal cancer disease management and treatment strategies. This work compared proteomic differences in OAC patients who responded well to chemotherapy as compared to those who did not, using quantitative proteomics prior to treatment commencement. SWATH-MS analysis of plasma (with and without albumin/IgG-depletion) from OAC patients prior to chemotherapy was performed. This approach was adopted to determine whether depletion offered a significant improvement in peptide coverage. Resultant datasets demonstrated that depletion increased peptide coverage significantly. Additionally, there was good quantitative agreement between commonly observed peptides. Data analysis was performed by adopting both univariate as well as multivariate analysis strategies. Differentially abundant proteins were identified between treatment response groups based on tumour regression grade. Such proteins included complement C1q sub-components and GSTP1. This study provides a platform for further work, utilising larger sample sets across different treatment regimens for oesophageal cancer, that will aid the development of 'treatment response prediction assays' for stratification of OAC patients prior to chemotherapy.

ALTEN: A High-Fidelity Primary Tissue-Engineering Platform to Assess Cellular Responses Ex Vivo

To fully investigate cellular responses to stimuli and perturbations within tissues, it is essential to replicate the complex molecular interactions within the local microenvironment of cellular niches. Here, the authors introduce Alginate-based tissue engineering (ALTEN), a biomimetic tissue platform that allows ex vivo analysis of explanted tissue biopsies. This method preserves the original characteristics of the source tissue's cellular milieu, allowing multiple and diverse cell types to be maintained over an extended period of time. As a result, ALTEN enables rapid and faithful characterization of perturbations across specific cell types within a tissue. Importantly, using single-cell genomics, this approach provides integrated cellular responses at the resolution of individual cells. ALTEN is a powerful tool for the analysis of cellular responses upon exposure to cytotoxic agents and immunomodulators. Additionally, ALTEN's scalability using automated microfluidic devices for tissue encapsulation and subsequent transport, to enable centralized high-throughput analysis of samples gathered by large-scale multicenter studies, is shown.

CST6 protein and peptides inhibit breast cancer bone metastasis by suppressing CTSB activity and osteoclastogenesis

Background: Bone metastasis is a frequent symptom of breast cancer and current targeted therapy has limited efficacy. Osteoclasts play critical roles to drive osteolysis and metastatic outgrowth of tumor cells in bone. Previously we identified CST6 as a secretory protein significantly downregulated in bone-metastatic breast cancer cells. Functional analysis showed that CST6 suppresses breast-to-bone metastasis in animal models. However, the functional mechanism and therapeutic potential of CST6 in bone metastasis is unknown.

Methods: Using in vitro osteoclastogenesis and in vivo metastasis assays, we studied the effect and mechanism of extracellular CST6 protein in suppressing osteoclastic niches and bone metastasis of breast cancer. A number of peptides containing the functional domain of CST6 were screened to inhibit bone metastasis. The efficacy, stability and toxicity of CST6 recombinant protein and peptides were evaluated in preclinical metastasis models.

Results: We show here that CST6 inhibits osteolytic bone metastasis by inhibiting osteoclastogenesis. Cancer cell-derived CST6 enters osteoclasts by endocytosis and suppresses the cysteine protease CTSB, leading to up-regulation of the CTSB hydrolytic substrate SPHK1. SPHK1 suppresses osteoclast maturation by inhibiting the RANKL-induced p38 activation. Importantly, recombinant CST6 protein effectively suppresses bone metastasis in vitro and in vivo. We further identified several peptides mimicking the function of CST6 to suppress cancer cell-induced osteoclastogenesis and bone metastasis. Pre-clinical analyses of CTS6 recombinant protein and peptides demonstrated their potentials in treatment of breast cancer bone metastasis.

Conclusion: These findings reveal the CST6-CTSB-SPHK1 signaling axis in osteoclast differentiation and provide a promising approach to treat bone diseases with CST6-based peptides.

A Pan-Cancer Analysis of Cystatin E/M Reveals Its Dual Functional Effects and Positive Regulation of Epithelial Cell in Human Tumors

Cystatin E/M (CST6), a representative cysteine protease inhibitor, plays both tumor-promoting and tumor-suppressing functions and is pursued as an epigenetically therapeutic target in special cancer types. However, a comprehensive and systematic analysis for CST6 in pan-cancer level is still lacking. In the present study, we explored the expression pattern of CST6 in multiple cancer types across ∼10,000 samples from TCGA (The Cancer Genome Atlas) and ∼8,000 samples from MMDs (Merged Microarray-acquired Datasets). We found that the dynamic expression alteration of CST6 was consistent with dual function in different types of cancer. In addition, we observed that the expression of CST6 was globally regulated by the DNA methylation in its promoter region. CST6 expression was positively correlated with the epithelial cell infiltration involved in epithelial-to-mesenchymal transition (EMT) and proliferation. The relationship between CST6 and tumor microenvironment was also explored. In particular, we found that CST6 serves a protective function in the process of melanoma metastasis. Finally, the clinical association analysis further revealed the dual function of CST6 in cancer, and a combination of the epithelial cell infiltration and CST6 expression could predict the prognosis for SKCM patients. In summary, this first CST6 pan-cancer study improves the understanding of the dual functional effects on CST6 in different types of human cancer.

Cystatin M/E (Cystatin 6): A Janus-Faced Cysteine Protease Inhibitor with Both Tumor-Suppressing and Tumor-Promoting Functions

Alongside its contribution in maintaining skin homeostasis and its probable involvement in fetal and placental development, cystatin M/E (also known as cystatin 6) was first described as a tumor suppressor of breast cancer. This review aims to provide an update on cystatin M/E with particular attention paid to its role during tumorigenesis. Cystatin M/E, which is related to type 2 cystatins, displays the unique property of being a dual tight-binding inhibitor of both legumain (also known as asparagine endopeptidase) and cysteine cathepsins L, V and B, while its expression level is epigenetically regulated via the methylation of the CST6 promoter region. The tumor-suppressing role of cystatin M/E was further reported in melanoma, cervical, brain, prostate, gastric and renal cancers, and cystatin M/E was proposed as a biomarker of prognostic significance. Contrariwise, cystatin M/E could have an antagonistic function, acting as a tumor promoter (e.g., oral, pancreatic cancer, thyroid and hepatocellular carcinoma). Taking into account these apparently divergent functions, there is an urgent need to decipher the molecular and cellular regulatory mechanisms of the expression and activity of cystatin M/E associated with the safeguarding homeostasis of the proteolytic balance as well as its imbalance in cancer.

Investigation of the clinical significance and prospective molecular mechanisms of cystatin genes in patients with hepatitis B virus‑related hepatocellular carcinoma

The present study aimed to investigate the clinical significance and prospective molecular mechanism of cystatin (CST) genes in patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). The role of CST genes in the molecular mechanism of HCC was revealed through bioinformatics analysis. The clinical significance of CST genes was investigated using GSE14520-derived data from patients with HBV-related HCC. Gene set enrichment analysis (GSEA) was used to identify pathways in which the CST genes were enriched, as well as the association between these pathways and HCC. The expression levels of CST1, CST2, CST5, CSTA and CSTB genes were higher in HCC tissue compared with in normal tissue; conversely, CST3 and CST7 were reduced in HCC tissue. Subsequent receiver operating characteristic analysis of the CST genes demonstrated that CST7 and CSTB genes may function as potential diagnostic markers for HCC. Furthermore, the expression levels of CST6 and CST7 were strongly associated with recurrence-free survival and overall survival of patients with HBV-related HCC. GSEA of the CST genes revealed that CST7 was significantly enriched in tumor evasion and tolerogenicity, cancer progenitors, liver cancer late recurrence, liver cancer progression and several liver cancer subclasses. In addition, CST genes demonstrated homology in terms of protein structure and were revealed to be strongly co-expressed. The present findings suggested that CST7 and CSTB genes may serve as potential prognostic and diagnostic biomarkers for HCC.

Cystatins in cancer progression: More than just cathepsin inhibitors

Cystatins are endogenous and reversible inhibitors of cysteine peptidases that are important players in cancer progression. Besides their primary role as regulators of cysteine peptidase activity, cystatins are involved in cancer development and progression through proteolysis-independent mechanisms. Mechanistic studies of cystatin function revealed that they affect all stages of cancer progression including tumor growth, apoptosis, invasion, metastasis and angiogenesis. Recently, the involvement of cystatins in the antitumor immune responses was reported. In this review, we discuss molecular mechanisms and clinical aspects of cystatins in cancer. Altered expression of cystatins in cancer resulting in harmful excessive cysteine peptidase activity has been a subject of several studies in order to find correlations with clinical outcome and therapy response. However, involvement in anti-tumor immune response and signaling cascades leading to cancer progression designates cystatins as possible targets for development of new anti-tumor drugs.

Cathepsins: Potent regulators in carcinogenesis

Cathepsins (CTS) are mainly lysosomal acid hydrolases extensively involved in the prognosis of different diseases, and having a distinct role in tumor progression by regulating cell proliferation, autophagy, angiogenesis, invasion, and metastasis. As all these processes conjunctively lead to cancer progression, their site-specific regulation might be beneficial for cancer treatment. CTS regulate activation of the proteolytic cascade and protein turnover, while extracellular CTS is involved in promoting extracellular matrix degradation and angiogenesis, thereby stimulating invasion and metastasis. Despite cancer regulation, the involvement of CTS in cellular adaptation toward chemotherapy and radiotherapy augments their therapeutic potential. However, lysosomal permeabilization mediated cytosolic translocation of CTS induces programmed cell death. This complex behavior of CTS generates the need to discuss the different aspects of CTS associated with cancer regulation. In this review, we mainly focused on the significance of each cathepsin in cancer signaling and their targeting which would provide noteworthy information in the context of cancer biology and therapeutics.

Tumor Sidedness and Enriched Gene Groups for Efficacy of First-line Cetuximab Treatment in Metastatic Colorectal Cancer

Molecular differences in tumor locations may contribute to the sidedness-specific response to cetuximab in metastatic colorectal cancer (mCRC). We investigated genes associated with the response to cetuximab treatment depending on tumor sidedness. Our study included 77 patients with mCRC (13/63, right/left) with KRAS exon 2 wild-type tumors from phase II trials of first-line therapy with cetuximab. Expression levels of 2,551 genes were measured in tissue samples by HTG EdgeSeq Oncology Biomarker Panel. Univariate Cox regression analysis using log₂ values of counts per million (CPM) was conducted in each sidedness to assess associations with clinical outcomes, and to define the optimal cut-off point for clinically significant genes. In addition, a gene set enrichment analysis (GSEA) was performed to identify significant gene pathways in each sidedness. Sixty-nine patients were assessable for gene expression data. Overexpression of BECN1 [log₂(CPM) ≥ 6.8] was associated with favorable survival, regardless of tumor sidedness. High expression of NOTCH1 [log₂(CPM) ≥ 7.5] predicted significantly longer progression-free survival (PFS; median 14.7 vs. 11.1 months, HR 0.43, P = 0.01) and overall survival (OS; median 42.8 vs. 26.5 months, HR 0.35, P = 0.01) in left side but not in right side. The GSEA showed that regulation of DNA replication gene set correlated with favorable survival in the left, whereas the subcellular component and leukocyte migration gene sets were associated with good survival in the right. In conclusion, genes contributing to the efficacy of cetuximab treatment may differ according to the sidedness in mCRC. NOTCH1 may potentially discriminate favorable responders to cetuximab in patients with left-sided tumors.

Cysteine cathepsins as a prospective target for anticancer therapies-current progress and prospects

Cysteine cathepsins (CTS), being involved in both physiological and pathological processes, play an important role in the human body. During the last 30 years, it has been shown that CTS are highly upregulated in a wide variety of cancer types although they have received a little attention as a potential therapeutic target as compared to serine or metalloproteinases. Studies on the increasing problem of neoplastic progression have revealed that secretion of cell-surface- and intracellular cysteine proteases is aberrant in tumor cells and has an impact on their growth, invasion, and metastasis by taking part in tumor angiogenesis, in apoptosis, and in events of inflammatory and immune responses. Considering the role of CTS in carcinogenesis, inhibition of these enzymes becomes an attractive strategy for cancer therapy. The downregulation of natural CTS inhibitors (CTSsis), such as cystatins, observed in various types of cancer, supports this claim. The intention of this review is to highlight the relationship of CTS with cancer and to present illustrations that explain how some of their inhibitors affect processes related to neoplastic progression.

Integrated analysis of SNP, CNV and gene expression data in genetic association studies

Integrative approaches that combine multiple forms of data can more accurately capture pathway associations and so provide a comprehensive understanding of the molecular mechanisms that cause complex diseases. Association analyses based on single nucleotide polymorphism (SNP) genotypes, copy number variant (CNV) genotypes, and gene expression profiles are the 3 most common paradigms used for gene set/pathway enrichment analyses. Many work has been done to leverage information from 2 types of data from these 3 paradigms. However, to the best of our knowledge, there is no work done before to integrate the 3 paradigms all together. In this article, we present an integrated analysis that combine SNP, CNV, and gene expression data to generate a single gene list. We present different methods to compare this gene list with the other 3 possible lists that result from the combinations of the following pairs of data: SNP genotype with gene expression, CNV genotype with gene expression, and SNP genotype with CNV genotype. The comparison is done using 3 different cancer datasets and 2 different methods of comparison. Our results show that integrating SNP, CNV, and gene expression data give better association results than integrating any pair of 3 data.

A novel treatment approach for retinoblastoma by targeting epithelial growth factor receptor expression with a shRNA lentiviral system

OBJECTIVES

Non-invasive treatment options for retinoblastoma (RB), the most common malignant eye tumor among children, are lacking. Epithelial growth factor receptor (EGFR) accelerates cell proliferation, survival, and invasion of many tumors including RB. However, RB treatment by targeting EGFR has not yet been researched. In the current study, we investigated the effect of EGFR down-regulation on RB progression using shRNA lentiviral vectors.

MATERIALS AND METHODS

EGFR expression in Weri-Rb-1 cells was down-regulated by EGFR shRNA-bearing lentiviral vectors. Cell death, proliferation, cell cycle as well as invasion after EGFR down-regulation were determined. Further signaling pathway analysis was done by Western blot.

RESULTS

Our results revealed that EGFR shRNA could specifically down-regulate EGFR expression and down-regulation of this protein promoted cell death. Further analysis on cell cycle demonstrated that EGFR down-regulation also suppressed cell proliferation by arresting cells at G1 phase. Invasion analysis showed that EGFR down-regulation suppressed cell invasion and was correlated with alteration in the expression of matrix metalloproteinases 2 and 9. Further signaling pathway analysis revealed that EGFR down-regulation mediated RB progression was through PI3K/AKT/mTOR signaling pathway.

CONCLUSION

Our study revealed that EGFR down-regulation, through the PI3K/AKT/mTOR signaling pathway, could inhibit RB progression by promoting cell death while suppressing cell proliferation and invasion. The findings of our study indicated that down-regulation of EGFR using shRNA lentiviral vectors may offer a novel non-invasive treatment for RB.

In Silico Analysis Validates Proteomic Findings of Formalin-fixed Paraffin Embedded Cutaneous Squamous Cell Carcinoma Tissue

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) is a common type of skin cancer but there are no comprehensive proteomic studies on this entity.

MATERIALS AND METHODS

We employed liquid chromatography coupled with tandem mass spectrometry (MS/MS) using formalin-fixed paraffin-embedded (FFPE) cSCC material to study the tumor and normal skin tissue proteomes. Ingenuity Pathway Analysis (IPA) was used to interpret the role of altered proteins in cSCC pathophysiology. Results were validated using the Human Protein Atlas and Oncomine database in silico.

RESULTS

Of 1,310 unique proteins identified, expression of an average of 144 and 88 proteins were significantly (p<0.05) increased and decreased, respectively, in the tumor samples compared to their normal counterparts. IPA analysis revealed disruptions in proteins associated with cell proliferation, apoptosis, and migration. In silico analysis confirmed that proteins corresponding to 12 antibodies, and genes corresponding to 18 proteins were differentially expressed between the two categories, validating our proteomic measurements.

CONCLUSION

Label-free MS-based proteomics is useful for analyzing FFPE cSCC tissues.

miRNA-129-5p suppresses cell proliferation and invasion in lung cancer by targeting microspherule protein 1, E-cadherin and vimentin

Downregulation of microRNA-129 (miR-129) has been described in various types of cancer, however, the significance of miR-129 in lung cancer has not been investigated. The present study, for the first time, determined miR-129-5p expression levels in both lung cancer cell lines and primary lung cancer tissues and also studied the effect of miR-129-5p on the proliferation and invasiveness of lung cancer cells. The results showed that miR-129-5p expression was significantly reduced in both lung cancer cell lines and primary lung cancer tissues (P<0.05). Further research revealed that miR-129-5p could suppress the proliferation and invasion capability of lung cancer cells. Bioinformatics analysis suggested three cancer-related miR-129-5p target genes: Microspherule protein 1 (MCRS1), E-cadherin and vimentin. Further investigation via reverse transcription-quantitative polymerase chain reaction and western blot analysis showed that miR-129-5p was able to reduce the expression levels of MCRS1 and vimentin and enhance the expression of E-cadherin at both the messenger RNA and protein levels. The present results indicate that miR-129-5p is able to suppress lung cancer cell viability and invasion, which may occur via the modulating of MCRS1, E-cadherin and vimentin expression. These findings suggest that miR-129-5p may be a potential biomarker and/or treatment strategy for lung cancer.

Cystatin E/M Suppresses Tumor Cell Growth through Cytoplasmic Retention of NF-κB

We and others have shown that the cystatin E/M gene is inactivated in primary human tumors, pointing to its role as a tumor suppressor gene. However, the molecular mechanism of tumor suppression is not yet understood. Using plasmid-directed cystatin E/M gene overexpression, a lentivirus-mediated tetracycline-inducible vector system, and human papillomavirus 16 (HPV 16) E6 and E7 gene-immortalized normal human epidermal keratinocytes, we demonstrated intracellular and non-cell-autonomous apoptotic growth inhibition of tumor cell lines and that growth inhibition is associated with cytoplasmic retention of NF-κB. We further demonstrated decreased phosphorylation of IκB kinase (IKKβ) and IκBα in the presence of tumor necrosis factor alpha (TNF-α), confirming the role of cystatin E/M in the regulation of the NF-κB signaling pathway. Growth suppression of nude mouse xenograft tumors carrying a tetracycline-inducible vector system was observed with the addition of doxycycline in drinking water, confirming that the cystatin E/M gene is a tumor suppressor gene. Finally, immunohistochemical analyses of cervical carcinoma in situ and primary tumors have shown a statistically significant inverse relationship between the expression of cystatin E/M and cathepsin L and a direct relationship between the loss of cystatin E/M expression and nuclear expression of NF-κB. We therefore propose that the cystatin E/M suppressor gene plays an important role in the regulation of NF-κB.

Gene expression profiling and DNA methylation analyses of CTCs

A variety of molecular assays have been developed for CTCs detection and molecular characterization. Molecular assays are based on the nucleic acid analysis in CTCs and are based on total RNA isolation and subsequent mRNA quantification of specific genes, or isolation of genomic DNA that can be for DNA methylation studies and mutation analysis. This review is mainly focused on gene expression and methylation studies in CTCs in various types of cancer.

Cathepsin L targeting in cancer treatment

Proteolytic enzymes may serve as promising targets for novel therapeutic treatment strategies seeking to impede cancer progression and metastasis. One such enzyme is cathepsin L (CTSL), a lysosomal cysteine protease. CTSL upregulation, a common occurrence in a variety of human cancers, has been widely correlated with metastatic aggressiveness and poor patient prognosis. In addition, CTSL has been implicated to contribute to cancer-associated osteolysis, a debilitating morbidity affecting both life expectancy and the quality of life. In this review, we highlight the mechanisms by which CTSL contributes to tumor progression and dissemination and discuss the therapeutic utility of CTSL intervention strategies aimed at impeding metastatic progression and bone resorption.

TBX2 represses CST6 resulting in uncontrolled legumain activity to sustain breast cancer proliferation: a novel cancer-selective target pathway with therapeutic opportunities

TBX2 is an oncogenic transcription factor known to drive breast cancer proliferation. We have identified the cysteine protease inhibitor Cystatin 6 (CST6) as a consistently repressed TBX2 target gene, co-repressed through a mechanism involving Early Growth Response 1 (EGR1). Exogenous expression of CST6 in TBX2-expressing breast cancer cells resulted in significant apoptosis whilst non-tumorigenic breast cells remained unaffected. CST6 is an important tumor suppressor in multiple tissues, acting as a dual protease inhibitor of both papain-like cathepsins and asparaginyl endopeptidases (AEPs) such as Legumain (LGMN). Mutation of the CST6 LGMN-inhibitory domain completely abrogated its ability to induce apoptosis in TBX2-expressing breast cancer cells, whilst mutation of the cathepsin-inhibitory domain or treatment with a pan-cathepsin inhibitor had no effect, suggesting that LGMN is the key oncogenic driver enzyme. LGMN activity assays confirmed the observed growth inhibitory effects were consistent with CST6 inhibition of LGMN. Knockdown of LGMN and the only other known AEP enzyme (GPI8) by siRNA confirmed that LGMN was the enzyme responsible for maintaining breast cancer proliferation. CST6 did not require secretion or glycosylation to elicit its cell killing effects, suggesting an intracellular mode of action. Finally, we show that TBX2 and CST6 displayed reciprocal expression in a cohort of primary breast cancers with increased TBX2 expression associating with increased metastases. We have also noted that tumors with altered TBX2/CST6 expression show poor overall survival. This novel TBX2-CST6-LGMN signaling pathway, therefore, represents an exciting opportunity for the development of novel therapies to target TBX2 driven breast cancers.

Cathepsin B: multiple roles in cancer

Proteases, including intracellular proteases, play roles at many different stages of malignant progression. Our focus here is cathepsin B, a lysosomal cysteine cathepsin. High levels of cathepsin B are found in a wide variety of human cancers, levels that often induce secretion and association of cathepsin B with the tumor cell membrane. In experimental models, such as transgenic models of murine pancreatic and mammary carcinomas, causal roles for cathepsin B have been demonstrated in initiation, growth/tumor cell proliferation, angiogenesis, invasion, and metastasis. Tumor growth in transgenic models is promoted by cathepsin B in tumor-associated cells, for example, tumor-associated macrophages, as well as in tumor cells. In transgenic models, the absence of cathepsin B has been associated with enhanced apoptosis, yet cathepsin B also has been shown to contribute to apoptosis. Cathepsin B is part of a proteolytic pathway identified in xenograft models of human glioma; targeting only cathepsin B in these tumors is less effective than targeting cathepsin B in combination with other proteases or protease receptors. Understanding the mechanisms responsible for increased expression of cathepsin B in tumors and association of cathepsin B with tumor cell membranes is needed to determine whether targeting cathepsin B could be of therapeutic benefit.

Anti-proliferative activity of 25-hydroxyvitamin D3 in human prostate cells

1α-Hydroxylation of 25-hydroxyvitamin D3 is believed to be essential for its biological effects. In this study, we evaluated the biological activity of 25(OH)D3 itself comparing with the effect of cell-derived 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3). First, we measured the cell-derived 1α,25(OH)2D3 level in immortalized human prostate cell (PZ-HPV-7) using [(3)H]-25(OH)D3. The effects of the cell-derived 1α,25(OH)2D3 on vitamin D3 24-hydroxylase (CYP24A1) mRNA level and the cell growth inhibition were significantly lower than the effects of 25(OH)D3 itself added to cell culture. 25-Hydroxyvitamin D3 1α-hydroxylase (CYP27B1) gene knockdown had no significant effects on the 25(OH)D3-dependent effects, whereas vitamin D receptor (VDR) gene knockdown resulted in a significant decrease in the 25(OH)D3-dependent effects. These results strongly suggest that 25(OH)D3 can directly bind to VDR and exerts its biological functions. DNA microarray and real-time RT-PCR analyses suggest that semaphorin 3B, cystatin E/M, and cystatin D may be involved in the antiproliferative effect of 25(OH)D3.

Highly synergistic effect of sequential treatment with epigenetic and anticancer drugs to overcome drug resistance in breast cancer cells is mediated via activation of p21 gene expression leading to G2/M cycle arrest

Epigenetic alterations such as aberrant DNA methylation and histone modifications contribute substantially to both the cause and maintenance of drug resistance. These epigenetic changes lead to silencing of tumor suppressor genes involved in key DNA damage-response pathways, making drug-resistant cancer cells nonresponsive to conventional anticancer drug therapies. Our hypothesis is that treating drug-resistant cells with epigenetic drugs could restore the sensitivity to anticancer drugs by reactivating previously silenced genes. To test our hypothesis, we used drug-resistant breast cancer cells (MCF-7/ADR) and two epigenetic drugs that act via different mechanisms--5-aza-2'-deoxycytidine (decitabine, DAC), a demethylating agent, and suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor--in combination with doxorubicin. We show that the sequential treatment of resistant cells, first with an epigenetic drug (DAC), and then with doxorubicin, induces a highly synergistic effect, thus reducing the IC(50) of doxorubicin by several thousand fold. The sequential treatment caused over 90% resistant cells to undergo G2/M cell cycle arrest, determined to be due to upregulation of p21(WAF1/CIP1) expression, which is responsible for cell-cycle regulation. The induction of p21(WAF1/CIP1) correlated well with the depletion of DNA methyltransferase1 (DNMT1), an enzyme that promotes methylation of DNA, suggesting that the p21(WAF1/CIP1) gene may have been methylated and hence is inactive in MCF-7/ADR cells. Microarray analysis shows expression of several tumor suppressor genes and downregulation of tumor promoter genes, particularly in sequentially treated resistant cells. Sequential treatment was found to be significantly more effective than simultaneous treatment, and DAC was more effective than SAHA in overcoming doxorubicin resistance. Synergistic effect with sequential treatment was also seen in drug-sensitive breast cancer cells, but the effect was significantly more pronounced in resistant cells. In conclusion, the sequential treatment of an epigenetic drug in combination with doxorubicin induces a highly synergistic effect that overcomes doxorubicin resistance in breast cancer cells.

Cystatins in immune system

Cystatins comprise a large superfamily of related proteins with diverse biological activities. They were initially characterised as inhibitors of lysosomal cysteine proteases, however, in recent years some alternative functions for cystatins have been proposed. Cystatins possessing inhibitory function are members of three families, family I (stefins), family II (cystatins) and family III (kininogens). Stefin A is often linked to neoplastic changes in epithelium while another family I cystatin, stefin B is supposed to have a specific role in neuredegenerative diseases. Cystatin C, a typical type II cystatin, is expressed in a variety of human tissues and cells. On the other hand, expression of other type II cystatins is more specific. Cystatin F is an endo/lysosome targeted protease inhibitor, selectively expressed in immune cells, suggesting its role in processes related to immune response. Our recent work points on its role in regulation of dendritic cell maturation and in natural killer cells functional inactivation that may enhance tumor survival. Cystatin E/M expression is mainly restricted to the epithelia of the skin which emphasizes its prominent role in cutaneous biology. Here, we review the current knowledge on type I (stefins A and B) and type II cystatins (cystatins C, F and E/M) in pathologies, with particular emphasis on their suppressive vs. promotional function in the tumorigenesis and metastasis. We proposed that an imbalance between cathepsins and cystatins may attenuate immune cell functions and facilitate tumor cell invasion.

Intra- and extracellular regulation of activity and processing of legumain by cystatin E/M

Legumain, an asparaginyl endopeptidase, is up-regulated in tumour and tumour-associated cells, and is linked to the processing of cathepsin B, L, and proMMP-2. Although legumain is mainly localized to the endosomal/lysosomal compartments, legumain has been reported to be localized extracellularly in the tumour microenvironment and associated with extracellular matrix and cell surfaces. The most potent endogenous inhibitor of legumain is cystatin E/M, which is a secreted protein synthesised with an export signal. Therefore, we investigated the cellular interplay between legumain and cystatin E/M. As a cell model, HEK293 cells were transfected with legumain cDNA, cystatin E/M cDNA, or both, and over-expressing monoclonal cell lines were selected (termed M38L, M4C, and M3CL, respectively). Secretion of prolegumain from M38L cells was inhibited by treatment with brefeldin A, whereas bafilomycin A1 enhanced the secretion. Cellular processing of prolegumain to the 46 and 36 kDa enzymatically active forms was reduced by treatment with either substance alone. M38L cells showed increased, but M4C cells decreased, cathepsin L processing suggesting a crucial involvement of legumain activity. Furthermore, we observed internalization of cystatin E/M and subsequently decreased intracellular legumain activity. Also, prolegumain was shown to internalize followed by increased intracellular legumain processing and activation. In addition, in M4C cells incomplete processing of the internalized prolegumain was observed, as well as nuclear localized cystatin E/M. Furthermore, auto-activation of secreted prolegumain was inhibited by cystatin E/M, which for the first time shows a regulatory role of cystatin E/M in controlling both intra- and extracellular legumain activity.

DNA methylation of tumor suppressor and metastasis suppressor genes in circulating tumor cells

BACKGROUND

Circulating tumor cells (CTCs) are associated with prognosis in a variety of human cancers and have been proposed as a liquid biopsy for follow-up examinations. We show that tumor suppressor and metastasis suppressor genes are epigenetically silenced in CTCs isolated from peripheral blood of breast cancer patients.

METHODS

We obtained peripheral blood from 56 patients with operable breast cancer, 27 patients with verified metastasis, and 23 healthy individuals. We tested DNA extracted from the EpCAM-positive immunomagnetically selected CTC fraction for the presence of methylated and unmethylated CST6, BRMS1, and SOX17 promoter sequences by methylation-specific PCR (MSP). All samples were checked for KRT19 (keratin 19, formerly CK-19) expression by reverse-transcription quantitative PCR.

RESULTS

In CTCs of patients with operable breast cancer, promoter methylation of CST6 was observed in 17.9%, BRMS1 in 32.1%, and SOX17 in 53.6% of patients. In CTCs of patients with verified metastasis, promoter methylation of CST6 was observed in 37.0%, BRMS1 in 44.4%, and SOX17 in 74.1%. In healthy individuals, promoter methylation of CST6 was observed in 4.3%, BRMS1 in 8.7%, and SOX17 in 4.3%. DNA methylation of these genes for both operable and metastatic breast cancer was significantly different from that of the control population.

CONCLUSIONS

DNA methylation of tumor suppressor and metastasis suppressor genes is a hallmark of CTCs and confirms their heterogeneity. Our findings add a new dimension to the molecular characterization of CTCs and may underlie the acquisition of malignant properties, including their stem-like phenotype.

Inhibition of invasion and metastasis of MHCC97H cells by expression of snake venom cystatin through reduction of proteinases activity and epithelial-mesenchymal transition

Snake venom cystatin (sv-cystatin) is a member of the cystatin family of cysteine protease inhibitors. To further evaluate the possibility of sv-cystatin in cancer therapy, this study examined the effects of sv-cystatin on the invasion and metastasis of liver cancer cells (MHCC97H) in vitro and in vivo as well as the underlying mechanism. sv-cystatin cDNA was transfected into MHCC97H cells and the anti-invasion and antimetastasis effects of sv-cystatin were determined using migration and matrigel invasion assays and a lung-metastasis mice model. The results suggest that sv-cyst clone (sv-cystatin expression in MHCC97H cells) delayed the invasion and metastasis in vitro and in vivo compared to the parental, mock and si-sv-cyst clone cells (inhibited sv-cystatin expression by siRNA). The decreased activities of cathepsin B, MMP-2 and MMP-9 and EMT change index including higher E-cadherin, lower N-cadherin and decreased Twist activity were observed in the sv-cyst clone, which contributes to the change in invasion and metastasis ability of MHCC97H cells. This study provides evidence that expression of the sv-cystatin gene in MHCC97H cells inhibits tumor cell invasion and metastasis through the reduction of the proteinases activity and Epithelial-Mesenchymal Transition (EMT), which might contribute to the anticancer research of the sv-cystatin protein.

Recombinant snake venom cystatin inhibits the growth, invasion and metastasis of B16F10 cells and MHCC97H cells in vitro and in vivo

Studies have shown that expression of snake venom cystatin (sv-cystatin) in mouse melanoma cells and human gastric carcinoma cells can inhibit their invasion and metastasis. To advance the research into the biological features and pharmaceutical applications of sv-cystatin, we investigated the expression of recombinant sv-cystatin in an optimized Pichia pastoris system. Approximately 5 mg/L of bioactive sv-cystatin was obtained with a purity of 95.08%. Kinetic analyses of recombinant sv-cystatin revealed highly effective inhibitory efficiency against papain (Ki = 2.67 nM). We further investigated the effects of recombinant sv-cystatin on the invasion and metastasis of B16F10 cells and MHCC97H cells in vitro and in vivo. Matrigel invasion assays showed significant inhibition of recombinant sv-cystatin on the tumor cells in vitro. For experimental lung colonization assays, C57BL/6 mice inoculated in the lateral tail vein with B16F10 cells were treated with three i.v. injections of recombinant sv-cystatin (25 and 50 mg/kg) 24 h before cell inoculation, and 2 h and 24 h after cell inoculation. Administration of recombinant sv-cystatin significantly suppressed the formation of lung tumor colonies. For spontaneous metastasis assays, MHCC97H cells were inoculated s.c. into nude mice. After 24 h, recombinant sv-cystatin was administered by i.p. injections at 25, 50 or 100 mg/kg once daily for 5 days. Administration of recombinant sv-cystatin significantly decreased the formation of lung tumor colonies. Taken together, recombinant sv-cystatin inhibits the invasion and metastasis of tumor cells in vitro and in vivo. These results may facilitate the future evaluation of the pharmaceutical applications of sv-cystatin.

The neuronal pentraxin II gene (NPTX2) inhibit proliferation and invasion of pancreatic cancer cells in vitro

The neuronal pentraxin II gene (NPTX2) is expressed in numerous tissues, such as the pancreas and the liver. While its activity in the brain is known to be regulated by neuronal activity, its function in the pancreas is unclear. In this study, we investigated the impact of NPTX2 on the proliferation, migration, invasion, apoptosis, and cell cycle of the pancreatic cancer cells. The expression levels of NPTX2 and their relation to the methylation level of the NPTX2 gene promoter in five pancreatic cancer cell lines were observed. The lower expression of NPTX2 in the cells was restored after the treatment of DNA methyltransferase inhibitor (5-aza-2'-deoxycytidine). Additionally, a full-length NPTX2 cDNA was transfected into pancreatic cancer cells (PANC-1) and we obtained the stably transfected cells (PANC-1-NPTX2). The ectopic NPTX2 expression significantly promoted G0-G1 arrest and cell apoptosis, and reduced cell proliferation, migration and invasion. Notably, the pro-apoptotic gene bax expression was significantly up-regulated while pro-survival gene bcl-2 did not significantly change in the stably transfected cells. Meanwhile, Cyclin D1 was significantly down-regulated. This study suggests that NPTX2, as a tumor-suppressor, plays an anti-tumor effect on pancreatic cancer and its low expression, due to promoter hypermethylation, may play a role in the tumorigenesis of pancreatic cancer.

Cystatin M loss is associated with the losses of estrogen receptor, progesterone receptor, and HER4 in invasive breast cancer

Introduction

This study was aimed at understanding the clinicopathological significance of cystatin M loss, and investigating possible factors responsible for cystatin M loss in breast cancer.

Methods

The expression of estrogen receptor (ER), progesterone receptor (PR), HER2, HER4, and cystatin M was retrospectively analyzed using immunohistochemistry in 117 patients with ductal carcinoma in situ (DCIS) and in 175 patients with invasive breast cancer (IBC). The methylation status of CST6 gene encoding cystatin M was evaluated using methylation-specific polymerase chain reaction (PCR) in formalin-fixed paraffin-embedded tissues from 292 participants and using pyrosequencing in fresh-frozen tumor and matched normal tissues from 51 IBC patients.

Results

Cystatin M loss was found in 9 (8%) of 117 patients with DCIS and in 99 (57%) of 175 with invasive breast cancer (IBC) (P < 0.0001). Cystatin M loss was found in 58 (57%) of 101 HER2-negative IBCs and in 41 (55%) of 74 HER2-positive IBCs, and this difference was not statistically significant (P = 0.97). However, cystatin M loss was significantly associated with the loss of ER (P = 0.01), PR (P = 0.002), and HER4 (P = 0.003) in IBCs. Cystatin M loss occurred in 34 (76%) of the 45 HER4-negative IBCs and in 65 (50%) of the 130 HER4-positive IBCs. Multivariate analysis showed that cystatin M loss occurred at a 3.57 times (95% CI = 1.28 to 9.98; P = 0.01) higher prevalence in the triple-negative IBCs of ER, PR, and HER4 than in other subtypes, after adjusting for age. The quantity of CST6 methylation was associated with ER loss (P = 0.0002) in IBCs but not with the loss of PR (P = 0.64) or HER4 (P = 0.87).

Conclusions

The present study suggests that cystatin M loss may be associated with the losses of ER, PR, and HER4 in IBC.

Identification of the amyloid β-protein precursor and cystatin C as novel epidermal growth factor receptor regulated secretory proteins in nasopharyngeal carcinoma by proteomics

The epidermal growth factor receptor (EGFR) is usually overexpressed in nasopharyngeal carcinoma (NPC) and is associated with pathogenesis of NPC. However, while EGFR-modulated intracellular proteins have been extensively studied, little is known concerning their extracellular counterparts. To identify EGFR-regulated secreted proteins in NPC, we compared the secretome profiles of TGF-α-stimulated and unstimulated NPC cell line CNE-2. CNE-2 cells were cultured in the absence or presence of TGF-α for 24 h, and secreted proteins were obtained from conditioned serum-free media and enriched by ultrafiltration centrifugation. Using 2-DE and subsequent mass spectrometry, we identified 16 differential secreted proteins, among which the amyloid β-protein precursor (APP) was up-regulated and cystatin C was down-regulated after TGF-α stimulation. We further showed that the secretory changes of APP and cystatin C in CNE-2 after TGF-α stimulation could be abrogated by pretreatment of EGFR tyrosine kinase inhibitor PD153035 and PI3 kinase inhibitor Wortmannin, validating that APP and cystatin C are EGFR-regulated secreted proteins in NPC cells. Immunohistochemistry showed that the expression level of EGFR was positively correlated with the expression level of APP and negatively correlated with the expression level of cystatin C in NPC tissues, indicating that EGFR also regulates expression of APP and cystatin C in clinical NPC tissues. Furthermore, functional analysis showed that the growth and migration of CNE-2 cells decreased after neutralization of secretory APP in the medium using the anti-APP antibody. Our data provide substantial evidence that APP and cystatin C are target secreted proteins of EGFR in NPC, and upregulation of secretory APP by EGFR may be involved in the pathogenesis of NPC.

Identification of candidate tumour suppressor genes frequently methylated in renal cell carcinoma

Promoter region hyermethylation and transcriptional silencing is a frequent cause of tumour suppressor gene (TSG) inactivation in many types of human cancers. Functional epigenetic studies, in which gene expression is induced by treatment with demethylating agents, may identify novel genes with tumour-specific methylation. We used high-density gene expression microarrays in a functional epigenetic study of 11 renal cell carcinoma (RCC) cell lines. Twenty-eight genes were then selected for analysis of promoter methylation status in cell lines and primary RCC. Eight genes (BNC1, PDLIM4, RPRM, CST6, SFRP1, GREM1, COL14A1 and COL15A1) showed frequent (>30% of RCC tested) tumour-specific promoter region methylation. Hypermethylation was associated with transcriptional silencing. Re-expression of BNC1, CST6, RPRM and SFRP1 suppressed the growth of RCC cell lines and RNA interference knock-down of BNC1, SFRP1 and COL14A1 increased the growth of RCC cell lines. Methylation of BNC1 or COL14A1 was associated with a poorer prognosis independent of tumour size, stage or grade. The identification of these epigenetically inactivated candidate RCC TSGs can provide insights into renal tumourigenesis and a basis for developing novel therapies and biomarkers for prognosis and detection.

Cystatin E/M suppresses legumain activity and invasion of human melanoma

Background

High activity of cysteine proteases such as legumain and the cathepsins have been shown to facilitate growth and invasion of a variety of tumor types. In breast cancer, several recent studies have indicated that loss of the cysteine protease inhibitor cystatin E/M leads to increased growth and metastasis. Although cystatin E/M is normally expressed in the skin, its role in cysteine protease regulation and progression of malignant melanoma has not been studied.

Methods

A panel of various non-melanoma and melanoma cell lines was used. Cystatin E/M and C were analyzed in cell media by immunoblotting and ELISA. Legumain, cathepsin B and L were analyzed in cell lysates by immunoblotting and their enzymatic activities were analyzed by peptide substrates. Two melanoma cell lines lacking detectable secretion of cystatin E/M were transfected with a cystatin E/M expression plasmid (pCST6), and migration and invasiveness were studied by a Matrigel invasion assay.

Results

Cystatin E/M was undetectable in media from all established melanoma cell lines examined, whereas strong immunobands were detected in two of five primary melanoma lines and in two of six lines derived from patients with metastatic disease. Among the four melanoma lines secreting cystatin E/M, the glycosylated form (17 kD) was predominant compared to the non-glycosylated form (14 kD). Legumain, cathepsin B and L were expressed and active in most of the cell lines, although at low levels in the melanomas expressing cystatin E/M. In the melanoma lines where cystatin E/M was secreted, cystatin C was generally absent or expressed at a very low level. When melanoma cells lacking secretion of cystatin E/M were transfected with pCST6, their intracellular legumain activity was significantly inhibited. In contrast, cathepsin B activity was not affected. Furthermore, invasion was suppressed in cystatin E/M over-expressing melanoma cell lines as measured by the transwell Matrigel assay.

Conclusions

These results suggest that the level of cystatin E/M regulates legumain activity and hence the invasive potential of human melanoma cells.

Cystatin M expression is reduced in gastric carcinoma and is associated with promoter hypermethylation

Cystatin M is a secreted inhibitor of lysosomal cysteine proteases and increasing evidences indicate that it is a novel target for epigenetic silencing during mammary tumorigenesis. Aberrant promoter methylation is a well-known mechanism that participates in cystatin M silencing in breast cancer. However, the role of cystatin M in the gastric cancer remains to be elucidated. Immunohistochemistry was used to investigate the expression of cystatin M in 60 gastric carcinomas. Hypermethylation of cystatin M promoter was evaluated by the methylation-specific PCR (MSP) method in gastric carcinomas (tumor and paired adjacent non-tumor tissues). Reverse-transcriptase PCR and BSP were also performed on gastric cancer cell lines before and after treatment with 5-aza-2'-deoxycytidine (5-Aza-dC). Lost expression of cystatin M was observed in 42 of 60 (70%) gastric carcinomas. 55% (33 of 60) of primary tumors analyzed displayed cystatin M promoter hypermethylation, indicating that this aberrant characteristic is common in gastric malignancies. Moreover, a statistically significant inverse association was found between cystatin M methylation status and expression of the cystatin M protein in tumor tissues (p=0.027). We also found that patients with cystatin M promoter methylation had a significantly shorter survival time than those without this methylation (p=0.020). These results suggest that cystatin M promoter hypermethylation is one of the molecular mechanisms that accounts for reduced cystatin M gene expression in gastric carcinomas.

Methylation of cystatin M promoter is associated with unfavorable prognosis in operable breast cancer

The methylation status of cystatin M (CST6) gene in breast tumors was investigated and its prognostic significance as a novel breast cancer biomarker was evaluated. Using methylation-specific PCR (MSP), CST6 promoter methylation was examined in 134 formalin fixed paraffin-embedded tissues (FFPEs): 10 pairs of breast tumors and their surrounding normal tissues, 10 breast fibroadenomas, 11 normal breast tissues and 93 breast tumors. Methylation of CST6 promoter was observed in 2/21 (9.5%) noncancerous breast tissues, 1/10 (10%) benign breast tumors (fibroadenomas) and 52 (55.9%) operable breast cancer tumor samples. CST6 was rarely methylated in the normal tissue surrounding the tumor (10%). During the follow-up period, 24 (25.8%) patients relapsed and 19 (20.4%) died. CST6 methylation was detected in 19 (79.2%) of patients who relapsed and in 15 (78.9%) of patients who died. Disease-free-interval (DFI) and overall survival (OS) were significantly associated with CST6 promoter methylation (p=0.004 and p=0.001 respectively). Multivariate analysis revealed that CST6 methylation is an independent prognostic factor for DFI (HR=3.484; 95% CI: 1.155-10.511; p=0.027). and OS (HR=9.190; 95% CI: 1.989-42.454; p=0.004). CST6 promoter methylation status in tumor cells seems to provide important prognostic information in operable breast cancer and merits to be further evaluated and validated in a larger cohort of patients.

Cystatin D is a candidate tumor suppressor gene induced by vitamin D in human colon cancer cells

The active vitamin D metabolite 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] has wide but not fully understood antitumor activity. A previous transcriptomic analysis of 1alpha,25(OH)2D3 action on human colon cancer cells revealed cystatin D (CST5), which encodes an inhibitor of several cysteine proteases of the cathepsin family, as a candidate target gene. Here we report that 1alpha,25(OH)2D3 induced vitamin D receptor (VDR) binding to, and activation of, the CST5 promoter and increased CST5 RNA and protein levels in human colon cancer cells. In cells lacking endogenous cystatin D, ectopic cystatin D expression inhibited both proliferation in vitro and xenograft tumor growth in vivo. Furthermore, cystatin D inhibited migration and anchorage-independent growth, antagonized the Wnt/beta-catenin signaling pathway, and repressed c-MYC expression. Cystatin D repressed expression of the epithelial-mesenchymal transition inducers SNAI1, SNAI2, ZEB1, and ZEB2 and, conversely, induced E-cadherin and other adhesion proteins. CST5 knockdown using shRNA abrogated the antiproliferative effect of 1alpha,25(OH)2D3, attenuated E-cadherin expression, and increased c-MYC expression. In human colorectal tumors, expression of cystatin D correlated with expression of VDR and E-cadherin, and loss of cystatin D correlated with poor tumor differentiation. Based on these data, we propose that CST5 has tumor suppressor activity that may contribute to the antitumoral action of 1alpha,25(OH)2D3 in colon cancer.

Frequent loss of cystatin E/M expression implicated in the progression of prostate cancer

Cystatin E/M (CST6) is a natural inhibitor of lysosomal cysteine proteases. Recent studies have shown that experimental manipulation of CST6 expression alters the metastatic behavior of human breast cancer cells. However, the association of CST6 with prostate cancer invasion and progression remains unclear. Here, we show that CST6 is robustly expressed in normal human prostate epithelium, whereas its expression is downregulated in metastatic prostate cell lines and prostate tumor tissues. Treatment of metastatic prostate cell lines with the histone deacetylase inhibitor trichostatin A resulted in significant induction of CST6 mRNA levels and increased CST6 protein expression, indicating that epigenetic silencing may play a role in the loss of CST6 expression observed in prostate cancer. CST6 overexpression in human prostate cancer cells significantly reduced in vitro cell proliferation and matrigel invasion. Furthermore, the results from a bioluminescence tumor/metastasis model showed that the overexpression of CST6 significantly inhibits tumor growth and the incidence of lung metastasis. These results suggest that the downregulation of the CST6 gene is associated with promoter histone modifications and that this association plays an important role in prostate cancer progression during the invasive and metastatic stages of the disease.

The biology of cystatin M/E and its cognate target proteases

Cystatin M/E is a member of a superfamily of evolutionarily-related cysteine protease inhibitors that provide regulatory and protective functions against uncontrolled proteolysis by cysteine proteases. Although most cystatins are ubiquitously expressed, high levels of cystatin M/E expression are mainly restricted to the epithelia of the skin (epidermis, hair follicles, sebaceous glands, and sweat glands) and to a few extracutaneous tissues. The identification of its physiological targets and the localization of these proteases in skin have suggested a regulatory role for cystatin M/E in epidermal differentiation. In vitro biochemical approaches as well as the use of in vivo mouse models have revealed that cystatin M/E is a key molecule in a biochemical pathway that controls skin barrier formation by the regulation of both crosslinking and desquamation of the stratum corneum. Cystatin M/E directly controls the activity of cathepsin V, cathepsin L, and legumain, thereby regulating the processing of transglutaminases. Misregulation of this pathway by unrestrained protease activity, as seen in cystatin M/E-deficient mice, leads to abnormal stratum corneum and hair follicle formation, as well as to severe disturbance of skin barrier function. Here, we review the current knowledge on cystatin M/E in skin barrier formation and its potential role as a tumor suppressor gene.

Inactivation of the cystatin E/M tumor suppressor gene in cervical cancer

We have previously localized a cervical cancer tumor suppressor gene to a 300 kb interval of 11q13. Analysis of candidate genes revealed loss of expression of cystatin E/M, a lysosomal cysteine protease inhibitor, in 6 cervical cancer cell lines and 9 of 11 primary cervical tumors. Examination of the three exons in four cervical cancer cell lines, 19 primary tumors, and 21 normal controls revealed homozygous deletion of exon 1 sequences in one tumor. Point mutations were observed in six other tumors. Two tumors contained mutations at the consensus binding sites for cathepsin L, a lysosomal protease overexpressed in cervical cancer. Introduction of these two point mutations using site directed mutagenesis resulted in reduced binding of mutated cystatin E/M to cathepsin L. Although mutations were not observed in any cell lines, four cell lines and 12 of 18 tumors contained promoter hypermethylation. Reexpression of cystatin E/M was observed after 5'aza 2-deoxycytidiene and/or Trichostatin A treatment of cervical cancer cell lines, HeLa and SiHa, confirming promoter hypermethylation. Ectopic expression of cystatin E/M in these two cell lines resulted in growth suppression. There was also suppression of soft agar colony formation by HeLa cells expressing the cystatin E/M gene. Reexpression of cystatin E/M resulted in decreased intracellular and extracellular expression of cathepsin L. Overexpression of cathepsin L resulted in increased cell growth which was inhibited by the reintroduction of cystatin E/M. We conclude, therefore, that cystatin E/M is a cervical cancer suppressor gene and that the gene is inactivated by somatic mutations and promoter hypermethylation.

Invasion suppressor cystatin E/M (CST6): high-level cell type-specific expression in normal brain and epigenetic silencing in gliomas

DNA hypermethylation-mediated gene silencing is a frequent and early contributor to aberrant cell growth and invasion in cancer. Malignant gliomas are the most common primary brain tumors in adults and the second most common tumor in children. Morbidity and mortality are high in glioma patients because tumors are resistant to treatment and are highly invasive into surrounding brain tissue rendering complete surgical resection impossible. Invasiveness is regulated by the interplay between secreted proteases (eg, cathepsins) and their endogenous inhibitors (cystatins). In our previous studies we identified cystatin E/M (CST6) as a frequent target of epigenetic silencing in glioma. Cystatin E/M is a potent inhibitor of cathepsin B, which is frequently overexpressed in glioma. Here, we study the expression of cystatin E/M in normal brain and show that it is highly and moderately expressed in oligodendrocytes and astrocytes, respectively, but not in neurons. Consistent with this, the CST6 promoter is hypomethylated in all normal samples using methylation-specific PCR, bisulfite genomic sequencing, and pyrosequencing. In contrast, 78% of 28 primary brain tumors demonstrated reduced/absent cystatin E/M expression using a tissue microarray and this reduced expression correlated with CST6 promoter hypermethylation. Interestingly, CST6 was expressed in neural stem cells (NSC) and markedly induced upon differentiation, whereas a glioma tumor initiating cell (TIC) line was completely blocked for CST6 expression by promoter methylation. Analysis of primary pediatric brain tumor-derived lines also showed CST6 downregulation and methylation in nearly 100% of 12 cases. Finally, ectopic expression of cystatin E/M in glioma lines reduced cell motility and invasion. These results demonstrate that epigenetic silencing of CST6 is frequent in adult and pediatric brain tumors and occurs in TICs, which are thought to give rise to the tumor. CST6 methylation may therefore represent a novel prognostic marker and therapeutic target specifically altered in TICs.

Dynamic changes in messenger RNA profiles of bovine endometrium during the oestrous cycle

During the oestrous cycle, the bovine endometrium exhibits characteristic morphological and functional changes, which are mainly induced by progesterone (P(4)), oestrogens and oxytocin. We studied the response of the endometrium to this changing hormonal environment at the transcriptome level using a custom-made cDNA microarray. Endometrium samples were recovered from Simmental heifers on days 0 (oestrus), 3.5 (metoestrus), 12 (dioestrus) and 18. The latter group was divided into animals with high (late dioestrus) and low P(4) levels (preoestrus). Significance analysis of microarrays revealed 269 genes exhibiting significant changes in their transcript levels during the oestrous cycle in distinct temporal patterns. Two major types of expression profiles were observed, which showed the highest mRNA levels during the oestrus phase or the highest levels during the luteal phase respectively. A minor group of genes exhibited the highest mRNA levels on day 3.5. Gene ontology (GO) analyses revealed GO categories related to extracellular matrix remodelling, transport, and cell growth and morphogenesis enriched at oestrus, whereas immune response and particular metabolic pathways were overrepresented at dioestrus. Generation of gene interaction networks uncovered the genes possibly involved in endometrial remodelling (e.g. collagen genes, TNC, SPARC, MMP2, MEP1B, TIMP1, TIMP2, HTRA1), regulation of angiogenesis (e.g. ANGPTL2, TEK, NPY, AGT, EPAS1, KLF5 ), regulation of invasive growth (e.g. PCSK5, tight junction proteins, GRP, LGALS1, ANXA2, NOV, PLAT, MET, TDGF1, CST6, ITGB4), cell adhesion (e.g. MUC16, LGALS3BP) and embryo feeding (e.g. SLC1A1, SLC11A2, SLC16A1, SEPP1, ENPP1). Localisation of mRNA expression in the endometrium was analysed for CLDN4, CLDN10, TJP1, PCSK5, MAGED1, and LGALS1.

Internalization of cystatin C in human cell lines

Altered protease activity is considered important for tumour invasion and metastasis, processes in which the cysteine proteases cathepsin B and L are involved. Their natural inhibitor cystatin C is a secreted protein, suggesting that it functions to control extracellular protease activity. Because cystatins added to cell cultures can inhibit polio, herpes simplex and coronavirus replication, which are intracellular processes, the internalization and intracellular regulation of cysteine proteases by cystatin C should be considered. The extension, mechanism and biological importance of this hypothetical process are unknown. We investigated whether internalization of cystatin C occurs in a set of human cell lines. Demonstrated by flow cytometry and confocal microscopy, A‐431, MCF‐7, MDA‐MB‐453, MDA‐MB‐468 and Capan‐1 cells internalized fluorophore‐conjugated cystatin C when exposed to physiological concentrations (1 μm). During cystatin C incubation, intracellular cystatin C increased after 5 min and accumulated for at least 6 h, reaching four to six times the baseline level. Western blotting showed that the internalized inhibitor was not degraded. It was functionally intact and extracts of cells exposed to cystatin C showed a higher capacity to inhibit papain and cathepsin B than control cells (decrease in enzyme activity of 34% and 37%, respectively). The uptake of labelled cystatin C was inhibited by unlabelled inhibitor, suggesting a specific pathway for the internalization. We conclude that the cysteine protease inhibitor cystatin C is internalized in significant quantities in various cancer cell lines. This is a potentially important physiological phenomenon not previously described for this group of inhibitors.

Over-expression of cysteine proteinase inhibitor cystatin 6 promotes pancreatic cancer growth

Pancreatic ductal adenocarcinoma (PDAC) shows the worst mortality among the common malignancies and development of novel therapies for PDAC through identification of good molecular targets is an urgent issue. Among dozens of over-expressing genes identified through our gene-expression profile analysis of PDAC cells, we here report CST6 (Cystatin 6 or E/M) as a candidate of molecular targets for PDAC treatment. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemical analysis confirmed over-expression of CST6 in PDAC cells, but no or limited expression of CST6 was observed in normal pancreas and other vital organs. Knock-down of endogenous CST6 expression by small interfering RNA attenuated PDAC cell growth, suggesting its essential role in maintaining viability of PDAC cells. Concordantly, constitutive expression of CST6 in CST6-null cells promoted their growth in vitro and in vivo. Furthermore, the addition of mature recombinant CST6 in culture medium also promoted cell proliferation in a dose-dependent manner, whereas recombinant CST6 lacking its proteinase-inhibitor domain and its non-glycosylated form did not. Over-expression of CST6 inhibited the intracellular activity of cathepsin B, which is one of the putative substrates of CST6 proteinase inhibitor and can intracellularly function as a pro-apoptotic factor. These findings imply that CST6 is likely to involve in the proliferation and survival of pancreatic cancer probably through its proteinase inhibitory activity, and it is a promising molecular target for development of new therapeutic strategies for PDAC.

MicroRNA signature predicts survival and relapse in lung cancer

We investigated whether microRNA expression profiles can predict clinical outcome of NSCLC patients. Using real-time RT-PCR, we obtained microRNA expressions in 112 NSCLC patients, which were divided into the training and testing sets. Using Cox regression and risk-score analysis, we identified a five-microRNA signature for the prediction of treatment outcome of NSCLC in the training set. This microRNA signature was validated by the testing set and an independent cohort. Patients with high-risk scores in their microRNA signatures had poor overall and disease-free survivals compared to the low-risk-score patients. This microRNA signature is an independent predictor of the cancer relapse and survival of NSCLC patients.

Epigenetic silencing of the tumor suppressor cystatin M occurs during breast cancer progression

Cystatin M is a secreted inhibitor of lysosomal cysteine proteases. Several lines of evidence indicate that cystatin M is a tumor suppressor important in breast malignancy; however, the mechanism(s) that leads to inactivation of cystatin M during cancer progression is unknown. Inspection of the human cystatin M locus uncovered a large and dense CpG island within the 5' region of this gene (termed CST6). Analysis of cultured human breast tumor lines indicated that cystatin M expression is either undetectable or in low abundance in several lines; however, enhanced gene expression was measured in cells cultured on the DNA demethylating agent 5-aza-2'-deoxycytidine (5-aza-dC). Increased cystatin M expression does not correlate with a cytotoxic response to 5-aza-dC; rather, various molecular approaches indicated that the CST6 gene was aberrantly methylated in these tumor lines as well as in primary breast tumors. Moreover, 60% (12 of 20) of primary tumors analyzed displayed CST6 hypermethylation, indicating that this aberrant characteristic is common in breast malignancies. Finally, preinvasive and invasive breast tumor cells were microdissected from nine archival breast cancer specimens. Of the five tumors displaying CST6 gene methylation, four tumors displayed methylation in both ductal carcinoma in situ and invasive breast carcinoma lesions and reduced expression of cystatin M in these tumors was confirmed by immunohistochemistry. In summary, this study establishes that the tumor suppressor cystatin M is a novel target for epigenetic silencing during mammary tumorigenesis and that this aberrant event can occur before development of invasive breast cancer.

Methylation-dependent silencing of CST6 in primary human breast tumors and metastatic lesions

CST6 is a breast tumor suppressor gene that is expressed in normal breast epithelium, but is epigenetically silenced as a consequence of promoter hypermethylation in metastatic breast cancer cell lines. In the current study, we investigated the expression and methylation status of CST6 in primary breast tumors and lymph node metastases. 25/45 (56%) primary tumors and 17/20 (85%) lymph node metastases expressed significantly lower levels of cystatin M compared to normal breast tissue. Bisulfite sequencing demonstrated CST6 promoter hypermethylation in 11/23 (48%) neoplastic lesions analyzed, including 3/11 (27%) primary tumors and 8/12 (67%) lymph node metastases. In most cases (12/23, 52%), the expression of cystatin M directly reflected CST6 promoter methylation status. In remaining lesions (8/23, 35%) loss of cystatin M was not associated with CST6 promoter hypermethylation, indicating that other mechanisms can account for loss of CST6 expression. These results show that methylation-dependent silencing of CST6 occurs in a subset of primary breast cancers, but more frequently in metastatic lesions, possibly reflecting progression-related genomic events. To examine this possibility, primary breast tumors and matched lymph node metastases were analyzed. In 2/3 (67%) patients, primary tumors were positive for cystatin M and negative for CST6 promoter methylation, and matched metastatic lesions lacked cystatin M expression and CST6 was hypermethylated. This observation suggests that progression-related epigenetic alterations in CST6 gene expression can accompany metastatic spread from a primary tumor site. Overall, the results of the current investigation suggest that methylation-dependent epigenetic silencing of CST6 represents an important mechanism for loss of CST6 during breast tumorigenesis and/or progression to metastasis.

DNA methylation-dependent silencing of CST6 in human breast cancer cell lines

Cystatin M (CST6) is a candidate breast cancer tumor suppressor that is expressed in normal and premalignant breast epithelium, but not in metastatic breast cancer cell lines. CST6 is subject to epigenetic silencing in MCF-7 breast cancer cells related to methylation of the CpG island that encompasses the CST6 proximal promoter region and exon 1. In the current study, CST6 CpG island methylation and expression status was examined in a panel of breast cancer cell lines. Seven of 12 (58%) cell lines lack detectable expression of CST6 and treatment of these cells with 5-aza-2'-deoxycytidine resulted in a significant increase in CST6 expression, suggesting that the loss of expression may be related to methylation-dependent epigenetic silencing. Bisulfite sequencing of CST6 in a subset of breast cancer cell lines revealed CpG island hypermethylation in CST6-negative cells, and an absence of CpG island methylation in cells that express CST6. The extent of regional methylation was strongly associated with the lack of expression of CST6 among these cell lines. In particular, hypermethylation of the proximal promoter was significantly associated with CST6 gene silencing, and methylation of a number of individual CpGs was found to be statistically correlated with extinction of gene expression. These results establish a strong link between CST6 promoter hypermethylation and loss of CST6 expression in breast cancer cell lines, and suggest that methylation-dependent epigenetic silencing of CST6 may represent an important mechanism for loss of CST6 during breast carcinogenesis in vivo.

Frequent epigenetic inactivation of cystatin M in breast carcinoma

Cystatin M is a potent endogenous inhibitor of lysosomal cysteine proteases. In breast carcinoma, cystatin M expression is frequently downregulated. It has been shown that cystatin M expression suppressed growth and migration of breast cancer cells. We examined the methylation status of the CpG island promoter of cystatin M in four breast cancer cell lines (MDAMB231, ZR75-1, MCF7 and T47D), in 40 primary breast carcinoma and in corresponding normal tissue probes by combined bisulphite restriction analysis. To investigate the effects of cystatin M expression on the growth of breast carcinoma, cystatin M was transfected in T47D. The cystatin M promoter was highly methylated in all four-breast cancer cell lines. Primary breast tumours were significantly more frequently methylated compared to normal tissue samples (60 vs 25%; P=0.006 Fisher's exact test). Treatment of breast cancer cells with 5-aza-2'-deoxycytidine (5-Aza-CdR), reactivated the transcription of cystatin M. Transfection of breast carcinoma cells with cystatin M caused a 30% decrease in colony formation compared to control transfection (P=0.002). Our results show that cystatin M is frequently epigenetically inactivated during breast carcinogenesis and cystatin M expression suppresses the growth of breast carcinoma. These data suggest that cystatin M may encode a novel epigenetically inactivated candidate tumour suppressor gene.

Towards novel anti-cancer strategies based on cystatin function

Cystatins have recently emerged as important players in a multitude of physiological and patho-physiological settings that range from cell survival and proliferation, to differentiation, cell signaling and immunomodulation. This group of cysteine protease inhibitors forms a large super-family of proteins composed of one, two, three, and, in some species, more than three cystatin domains. Over the last 20 years or so, members of the cystatin super-family have been primarily explored with respect to their capacity to inhibit intracellular cysteine proteases. Yet, this classical mode of action does not fully explain their remarkably diverse biological functions. Due to the space limitations, the author will discuss here the most recent findings that suggest that some of the single-domain, cytoplasmic and cell-secreted cystatins may play important roles in the promotion or suppression of tumor growth, invasion and metastasis. Based on the present understanding of cystatin function, novel avenues for anti-cancer strategies are proposed.

Overexpression of stefin A in human esophageal squamous cell carcinoma cells inhibits tumor cell growth, angiogenesis, invasion, and metastasis

PURPOSE

Evidence is accumulating that an inverse correlation exists between stefin A level and malignant progression. The aim of this study is to investigate the role of stefin A in human esophageal squamous cell carcinoma cells and to evaluate the possibility of stefin A for cancer therapy.

EXPERIMENTAL DESIGN

We stably transfected stefin A cDNA into human EC9706 or KYSE150 esophageal squamous cell carcinoma cells. Subsequently, we evaluated the effect of stefin A overexpression on cell growth, cathepsin B activity, cell motility and invasion, tumor growth, and metastasis. Immunoanalysis was done to assess the expression of factor VIII and to support the localization of stefin A and cathepsin B. We also evaluated the effect of CA074Me, a selective membrane-permeant cathepsin B inhibitor.

RESULTS

Both transfection of stefin A and treatment with 10 micromol/L CA074Me significantly reduced cathepsin B activity and inhibited the Matrigel invasion. Combination of both further reduced cathepsin B activity and inhibited the Matrigel invasion. Overexpression of stefin A delayed the in vitro and in vivo growth of cells and significantly inhibited lung metastasis compared with 50% of lung metastasis in xenograft mice from EC9706 or empty vector cells. Transfection with stefin A showed a dramatic reduction of factor VIII staining in the tumors of xenograft mice.

CONCLUSIONS

Our data strongly indicate that stefin A plays an important role in the growth, angiogenesis, invasion, and metastasis of human esophageal squamous cell carcinoma cells and suggest that stefin A may be useful in cancer therapy.